This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Effective therapy for human immunodeficiency virus (HIV) infection has markedly prolonged survival in infected individuals. As a result, other comorbid conditions in these patients are becoming more clinically important. Approximately 30% of HIV infected patients are also infected with hepatitis C virus (HCV) which is now the leading co-morbid disease in HIV-infected individuals. The histologic severity and natural history of HCV is reported to be accelerated in those co-infected with HIV. Although treatment of HCV has improved, the response rates in co-infected individuals remains suboptimal. It is hypothesized that: 1) the severity and progression of hepatic fibrosis in patients with HIV-HCV coinfection is directly related to the immunologic competence of the individual, and 2) the virologic response to anti-HCV treatment is directly related to the degree of immunologic competence.